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Summary of the impact

Researchers in petroleum geology at the University of Aberdeen have since
the mid 1990's been
investigating the characteristics and geological context of sand
injectites. The geological contexts
within which injected sands are discovered have permitted a step change in
the production
potential in some oil fields (up to c. 1 billion barrels oil), and to
define new exploration targets (up to
250 million barrels oil) to make a significant increase to the overall
proven reserves of
hydrocarbons in any given province (e.g. the North Sea). The findings of
this research have been
utilised by a number of multinational oil & gas companies to optimise
their exploration and field
development strategies to maximise the commercial production of
hydrocarbons. This case study
describes the economic impacts resulting from two projects in particular
in the North Sea, the
Volund field (Marathon Oil) and the Mariner Field (Statoil) resulting in
the enhancement of strategy,
operations and management practices; improvements in performance and
adoption of new
processes; and creation of new employment as a direct result of research
facilitating the
development of new assets that would otherwise have remained fallow.

Underpinning research

Despite being described in a paper in 1827, sand injectites received
little attention and was given
almost no scientific or commercial attention for the next 170 years. The
paucity of scientific
understanding meant that any practical or commercial implications that
sand injectites might have
were overlooked. However, in 1998 high-quality 3D seismic reflection
surveys over the Alba oilfield
(Statoil/Chevron) revealed the common occurrence of sandstone intrusions
as entire or significant
components of oilfields, allowing the field development strategy for that
field to be optimised. Since
that time Professor Andrew Hurst has created the Sand Injectites Research
Group (SIRG) at the
University of Aberdeen to investigate these phenomena, and this group has
become the global
focus of knowledge for understanding the geological conditions that lead
to formation of sand
injectites, their significance in petroleum systems and, specifically,
their potential for holding
commercial volumes of hydrocarbon and hence as targets for exploration and
field-development
drilling. An invited 2007 Memoir (AAPG 87) documented the early stages of
research by SIRG and
associates, including oil industry partners. The Sand Injectites Research
Group (SIRG) has more
than 12 years continuous activity funded by the international oil industry
(BG, Cairn, Chevron, Det
Norske, DONG, EnQuest, JX Nippon, Kerr McGee, Lundin, Maersk, Marathon,
Premier Oil, Shell,
Statoil, Total, and Wintershall), to a total value of £2.2 million.

By examining never-previously-described outcrop and examining
oil-industry subsurface data (1,2)
SIRG developed predictive models for the occurrence and geometry of sand
injectites that
previously were deemed random (3). Through understanding the relationships
between sandstone
distribution and their mechanism of formation it was recognised that
regionally-developed instability
in the very shallow (<2 km burial) crust was caused by the focussing of
anomalously-high pore-
fluid pressure that caused the hydraulic fracture of low-permeability
strata and concomitant
fluidisation and upward injection of sand into the fractures. This group
of processes occur rapidly
(from days to weeks) and frequently mobilise 10-100's km3 of
sand. Such intrusions have occurred
in sedimentary basins globally throughout geologic time (2). As a result
of the research
undertaken, sand injectites are no longer considered to be occasional
anomalous features, but
often constitute the predominant occurrence of sandstone in many
petroleum-bearing basins, and
are hence of direct importance in hydrocarbon exploration and production.

SIRG's research has been undertaken through oil-industry-sponsored Joint
Industry Projects. Of
direct significance to hydrocarbon exploration-drilling SIRG's research
during phase 1 (2000-2003)
defined intrusive traps a new class (type) of hydrocarbon trap
(1). Specifically this stimulated
exploration for intrusive targets on the NW European Continental
Shelf and contributed to the
discovery (2003) and development of Volund field on the Norwegian
Continental Shelf (NCS) and
other exploration projects globally.

During phase 2 (2005-2009) SIRG's cross-disciplinary research team
determined the pore-fluid
pressures at which hydraulic failure occurred and the velocity, rheology
and turbulence of the
fluidised sand (3, 4). Thus for the first time the conditions of formation
of the external and internal
structures associated with sand injectites could be inferred (4, 5).
Relating the physical model to
characteristics of sand injectites preserved in the rock record provides
the key to understanding
why and if large-scale sand injection occurs and how to differentiate them
from depositional
sandstones when encountered in the subsurface, which is of critical
importance to the oil industry
when modelling the evolution of pore-fluid pressure and predicting
sandstone distribution in
petroleum systems. A further new hydrocarbon trap — extrusive — was
defined (6).

Current and future research (phase 3 commenced in 2013) examines in more
detail the
significance of sand injectites in basin/petroleum system evolution, in
particular focussing on
mechanisms for the development of regional pore-fluid overpressures in the
very shallow crust (5).
Elevation of pore-fluid pressure is the driver of hydraulic fracturing and
sand fluidisation.
Constraining the geological conditions under which it occurs will allow
better pre-drill prediction of
the likelihood of occurrence of sand injectites as both discrete
sedimentary units or as modifiers of
depositional units.

3. Vigorito, M. and Hurst, A. 2010. "Regional sand injectite
architecture as a record of pore
pressure evolution and sand redistribution in the shallow crust:
insights from the Panoche Giant
Injection Complex, California." Journal Geological Society of London
167, 889-904. This
included a critical evaluation of the relationship between pore-fluid
pressure and the architecture
and external geometry of a giant sand injection complex.

4. Hurst, A., Scott, A. and Vigorito, M. 2011. "Physical
characteristics of sand injectites, Earth-
Science." Reviews 106, 215-246. This is the first ever review of
the sand injectites and their
mechanism of formation.

5. Scott, A., Vigorito, M. and Hurst, A. 2009. "The process
of sand injection: internal structures and
relationships with host strata (Yellowbank Creek injectite complex,
California)." Journal of
Sedimentary Research 79, 568-583. This provided a detailed analysis of
the origin of granular
textures in a sandstone intrusion and their relationship to the process
of sand emplacement.

Details of the impact

Hurst and his collaborators have established a global reputation for
identifying the presence and
significance of sand injectites in petroleum systems. Direct practical
implications of the models
include:

a) improved pre-drill prediction of sandstone distribution that leads to
more successful
exploration;

b) more accurate and appropriate description and modelling of reservoirs
in which sandstone
intrusions occur;

c) targeting of "sand injectite exploration prospects" - intrusive
traps - by the direct application
of the scientific basis from their occurrence developed by SIRG;

d) definition of criteria for identifying sand injectites in boreholes
(Duranti and Hurst 2004) now in
widespread use in the oil industry and academia;

e) a programme of workshops and courses with industry partners to ensure
transfer of science
and technology into their environment.

New exploration and field-development drilling targets have been
identified that led to the
generation of completely new exploration plays, the discovery of new
oilfields and improved
recovery from existing oilfields. Currently several oil company sponsors,
including Marathon,
Premier Oil, Total and Statoil, amongst others, use SIRG's concepts and
data routinely in their
exploration programmes. Four case studies from these named companies offer
examples of this.

Marathon Oil participated in Phase 1 of the Sand Injectites research
programme. As a result of the
research findings concerned with intrusive traps Marathon discovered
Volund field in 2003, with an
expected gross value >$6Bn (7). Following discovery SIRG worked closely
with the Volund field
development team, supporting validation of quantitative models of oil
production and advising on
appropriate geological procedure for drilling (7). The Chief Geoscientist
at Marathon Oil has
confirmed that SIRG's "analogue data were a critical component of the
pre-exploration de-risking of
Volund and had a direct impact on the eventual approval to sanction
funding an exploration well
given by Marathon's Head Office, Houston" (2).

This exploration success prompted new sponsor involvement with an
injectite exploration focus.
Encore (now Premier Oil) have used the results of research to confirm the
production potential of
the greater Catcher field in 2010, and have commented that "EnCore's
discovery of Catcher,
Varadero and Burgman fields in Block 28/9 was the UK exploration success
story of 2010.......
there is believed to be 400mmbo [million barrels of oil equivalent]
in place" in which "Prof Hurst's
research has had immediate effect on our evaluation of the Greater
Catcher area and we plan to
develop our working relationship with him. It appears that Sand
Injectite research is a rather
special feature of UK geological research with high relevance to the oil
industry and well deserving
of international recognition" (3).

Statoil have financially supported Sand Injectites research from the
outset in the late 1990's. As a
result of research findings, Statoil were able to identify the widespread
presence of injected sands
within their field development areas, and were able to re-frame and
optimise their field
development strategies accordingly. The generic benefits of SIRG's
research to Statoil have been
summarised by a Senior Research Scientist (Exploration) for Statoil, in a
communication to the
University of Aberdeen: "Statoil recognised the lack of research on the
enigmatic but oftenregionally-developed features known as sand injectites. By investing in
the Sand Injectites
consortia at the University of Aberdeen Statoil has increased its
understanding of when, where and
how sand injectites form thus enhancing our understanding of their role
in basin evolution. Equally
important has been the generation of the first ever large outcrop
database of sand injectites that
helps all aspects of our subsurface evaluation, including seismic
interpretation, and reservoir
characterisation. In my daily work I use pictures and ideas from these
outcrops to educate and
illustrate how sand injectites are formed and expressed in the
subsurface" (1). Most recently
Statoil's development of the Mariner field in the UKCS has been approved,
with a field
development strategy based around exploitation of reserves within sand
injectites, which is a direct
consequence of collaboration with SIRG. The field is believed to hold
reserves of approximately
300 million barrels with a commercial value of some $8 billion. As a
result of this field development
700 new jobs will be created (6). Statoil have confirmed that the SIRG "group
has made tangible
contributions to Mariner's commerciality and allowed an appreciation of
the main uncertainties and
how to best geologically model them" (5). Whilst production from the
field will not commence until
2017, the impact generated from government approval of development plans
is considerable in
guaranteeing future economic returns.

In the context of oilfield development SIRG research has played an
important role supporting
operators with well placement and optimising hydrocarbon recovery. In
2002, prior to development
of Girasol (offshore Angola, 1.55 MMB OOIP), Total Research in Pau invited
SIRG to examine
core data from Girasol and other offshore fields/discoveries that "confirmed
the presence of
significant sub vertical sandstone intrusions ...... their
identification gave the possibility of much
higher than expected vertical permeability between the main sandstone
reservoirs and consequent
improved aquifer support. This interpretation proved to be correct and
participated to the
understanding of the oil production and water-handling characteristics
of Girasol" (4).

SIRG's transfer of research results to the oil industry is a prioritised
activity and has an increasingly
global impact. Company-specific workshops and field courses are also
common activities (in 2013
4 field trips are organised for the benefit of Premier Oil, Wintershall,
Cairn Energy, Maersk, Det
Norske, Statoil and Tullow Oil). Since 2008 approximately 150 oil-company
personnel have
attended field courses led by Hurst and colleagues and many more have
attended office-located
workshops. Courses are typically associated with specific oil fields or
are used to heighten the
awareness of sand injectites within companies.

Sources to corroborate the impact

A Senior Research Scientist (Exploration), Statoil Norway corroborates
the impact and benefits
generally of sand injectites research, and especially the early impact
related to the Alba field
development.

The Chief Geoscientist at Marathon Oil UK corroborates the impact and
benefits to Marathon of
the Volund field development.

A former member of staff at EnCore corroborates the impact and
benefits to the Catcher field
development.

Staff at Total E&P, Pau confirms the impact on the Girasol
development offshore Angola.

A member of staff at Statoil, Aberdeen confirms the impact and
benefits to the Mariner field
development.